My novel - the urban fantasy one I am currently editing after intensive beta reading - has a very strict structure. Three parts (because I love the three act structure), each containing seven chapters (because... I'm not actually sure). I laid it out like that when I started, and have stuck to it ever since.
In my last edit, a few conclusive plot developments got pushed off the end of the final chapter - Chapter Twenty-One, obviously - and I put them in an epilogue. Because this preserves my precious structure.
I've continued this game of sevens all the way to the fourth draft, and frankly I think I deserve a medal. Or at least a giant seven-shaped cake. You can probably find one in shops under Birthday Cakes For Seven Year Olds.
Still, all good things are determined to come to an end, and I don't think I can sustain this shape any longer. I've planned out my new final third and am adding some major new sections to the book, important new bits, cool stuff, all thanks to good suggestions from my excellent beta people. But I don't think I can do it within the seven/seven/seven framework - not without writing chapters that are also ten/twelve thousand word novellas, at least.
So, with a heavy heart and a grim smile, maybe ever a cinematic single tear, I am waving goodbye to the sevens. I will miss them, but anything that makes the book better is probably worth it. And I still have sevens in the first and second third.
And, ditching the faux-eulogy tone for a second, let's be honest: if an editor, agent, publisher or similar entity says I need to add extra chapters to the book anywhere, further messing up the sevens, I'll definitely do it as long as I agree it'll improve the story. Hardly seems practical to get over-attached to these things. Not as if the chapter-counts are story relevant, it just worked out that way.
And it least it gave me something to work within while I got the book written. Let's not be ungrateful.
I'm glad I wrote this blog post, it was therapeutic.